1. Field of Invention
The present invention relates generally to the field of oilfield exploration, production, and testing, and more specifically to swellable elastomeric materials and their uses in such ventures.
2. Related Art
Recently there has been a growing interest in swellable elastomers for use in oilfield applications. Oil-swellable packers are now on the market, as well as expandable zonal isolation profilers that use a water-swellable elastomer. There are reported to be water-swellable and oil-swellable packers on the market for oilfield applications, although it is not known if these packers swell in both oil and water.
Most commercially available elastomers exhibit a high resistance to swelling in water and brines, but are not too resistant to swelling in oils. Resistance to water and brine swelling is required for common non-oilfield applications like tires, hose, wire and cable applications, and the like. Many commonly used elastomers exhibit poor resistance to swelling in oil. Other elastomers such as nitrile, hydrogenated nitrile, fluoroelastomers and acrylate-based elastomers are designed to resist swelling in oil and are extensively used in oilfield applications; and are resistant to swelling in water and brine.
In order to make oil-swellable elastomers also swell in water, previous publications have disclosed blends of elastomers with superabsorbent polymers like hydrogels (Report #RUS 1-1464-ST-04, Institute of Rubber Coatings and Products, L. Akopyan, Moscow Research Center, and references therein). The main drawback of blending in hydrogels is that hydrogel-containing swellable polymers do not possess long term physical integrity. This is because the hydrogel particles that are initially embedded in the elastomer tend to migrate to the surface of the elastomer part and into the water phase. As a result the elastomer-hydrogel blend exhibits nonuniform swelling and develops blisters on the surface when exposed to water. After a few days of exposure to water these blisters burst open and hydrogel particles are ejected out of the blend leaving behind cracks in the elastomer. The hydrogel-filled elastomer swells when exposed to water but the hydrogel particles migrate to the surface of the elastomer causing the elastomer to develop blisters, fissures and eventual disintegration of the material. This makes hydrogel/elastomer blends unsuitable for long term application in oilfields.
Many oilfield elements and tools utilize elastomeric materials. For example, elastomers and other polymers may be used in packer elements, blow out preventer elements, submersible pump protectors (sometimes referred to as protector bags), O-rings, gaskets, electrical insulators, pressure sealing elements for fluids, and in many other oilfield elements.
Common to all of these uses of elastomers is exposure to hostile environments, such as hostile chemical and mechanical subterranean environments, that tend to unacceptably decrease the life and reliability of the elastomers. There remains a need in the natural resources exploration, production, and testing field for improving reliability and life, as well as electrical properties in some instances, of elastomeric components used in oilfield environments, such as protector bags, packer elements, pressure seals, valves, blow out preventer components, cable shielding and jacketing, and the like. It would be an advance in the art to develop elastomer compositions (and methods of making same) that swell but do not substantially degrade or disintegrate upon long term exposure to water and water-based fluids, such as brines, and optionally in hydrocarbon fluids.